As environmental friendly vehicles, electrically powered vehicles such as electric cars and hybrid cars are attracting great attention. These vehicles are equipped with a motor generating driving force for traveling, and a rechargeable power storage device storing electric power to be supplied to the motor. It is to be noted that hybrid cars include a vehicle further equipped with an internal combustion engine as a motive power source in addition to the motor, or a vehicle further equipped with a fuel cell as a direct current (DC) power source for driving the vehicle in addition to the power storage device.
Among the hybrid cars, a vehicle equipped with a power storage device that is chargeable from a power source external to the vehicle as in an electric car has been known. For example, a so-called “plug-in hybrid car”, in which a power storage device is chargeable from a general household power source by connecting an electrical outlet provided in a house and a charging inlet provided in the vehicle via a charging cable, has been known.
Meanwhile, as a method of transmitting electric power, wireless electric power transmission not using a power source cord or an electric power transmission cable has been attracting attention in recent years. As predominant techniques for such wireless electric power transmission, there are three known techniques: electric power transmission using electromagnetic induction, electric power transmission using an electromagnetic wave, and electric power transmission using a resonance method.
Among them, the resonance method is a noncontact electric power transmission technique in which a pair of resonators (for example, a pair of self-resonant coils) are caused to resonate in an electromagnetic field (a near field) to transmit electric power via the electromagnetic field. The method allows transmission of large electric power of several kW over a relatively long distance (for example, several meters) (Patent Document 1).    Patent Document 1: WO2007/008646